Source : Webster's Revised Unabridged Dictionary (1913)

Modifiable \Mod"i*fi`a*ble\, a. [From {Modify}.]
   Capable of being modified; liable to modification.

Source : WordNet®

modifiable
     adj : capable of being modified in form or character or strength
           (especially by making less extreme); "the rhythm of
           physiological time is not modifiable except by
           interference with certain fundamental processes" -
           Alexis Carrel [ant: {unmodifiable}]